1. Field of the Invention
The present invention relates to an electrical connector device.
Recent progress in requiring higher performance for computer systems includes the printed circuit boards used in these computer systems to be reduced in size and to have a high packing density.
Consistent with this recent progress, many input/output (I/O) pins are being implanted on one printed circuit board. However, attempts in connecting large amounts of I/O pins on the circuit board by using conventional male-female connectors for electrically connecting these printed circuit boards require a large amount of force on the printed circuit board. As a result, a large amount of force is applied on the printed circuit board when the male connector is fitted resulting in problems, such as, the printed circuit board being warped or in some cases, the printed circuit board being altogether broken.
Moreover, electronic parts, such as semiconductor elements, have been mounted on the printed circuit board in the form of bare chips. However, the printed circuit board having the electronic elements mounted thereon is generally formed of ceramic materials. The pads provided at predetermined regions of a bare chip of an electronic part are connected by solder with the pads provided at predetermined regions of the ceramic circuit board, but the difference of expansion coefficients between the ceramic substrate and the bare chip is large. Thus, when a bare chip is loaded or mounted on the printed circuit board, mechanical stress is generated at the junction area between the electronic parts and the printed circuit board due to temperature change at the time the power is turned ON and OFF, thereby cracks are sometimes generated at the soldered junction area.
2. Description of the Relevant Art
Attempts have been made in order to resolve the abovediscussed problems by using liquid metal for the contact area. This method is, for example, disclosed in the following patents: (1) Japanese Laid-Open Patent No. 52-73392 by H. Tsuji and K. Kawano; (2) Japanese Laid-open Patent No. 60-253177 by M. Yasunaga and K. Sato; and (3) Japanese Laid-open Patent No. 58-130540 by H. Doi et al.
In the Japanese Laid-Open Patent No. 52-73392, the contact (i.e., the junction area) is formed by a flexible material impregnated with liquid metal and the male-female connector is connected through this contact area.
In Japanese Laid-open Patent No. 60-253177, a solid metal is heated and converted to liquid metal, and electrical connection is formed by inserting electrodes to the liquid metal.
However, the metal used for the contact in Japanese Laid-Open Patent No. 52-73392 is always liquid, and the liquid metal splashes and is disabled while the terminal is repeatedly fitted and removed. In Japanese Laid-open Patent No. 60-253177, there is the disadvantage of having the liquid metal splash and consumed, like in Japanese Laid-Open Patent No. 52-73392, due to fitting and removal of electrodes. A heating apparatus is further required for melting the solid metal.
In the Japanese Laid-open Patent No. 58-130540, balls of liquid metal or liquid alloy are, under room temperature, adhered to a plurality of first pads provided at the predetermined surfaces of the electronic parts in the mounting of the electronic parts on the printed circuit board, and the first pads are positioned so that these balls match a plurality of second pads provided on the mounting surface of the printed circuit board. However, the procedural steps in forming many liquid balls and adhering these balls to the first pads cannot be easily done.
Accordingly, a conventional electrical connector cannot ensure reliable connection and the resulting efficiency for the mounting operation is low.